DME Gurus: What will removing the AFM do to the ignition timing?

[bmwman91]

Well, the rest of my MegaSquirt stuff is in the mail now (well, I will be ordering the WBO2 in a couple weeks when I have the $ for that) and as anyone familiar with it knows, the AFM is gonen be GONE (along with the ICV). Now I know that when the AFM is disconnected the Motronic DME will go into "limp" mode as far as fueling...it will run solely from the O2 sensor input and some "safe" fuel maps (very rich to prevent detonation).

Here is the big question...
Will it continue to use the "normal" timing maps, or will it cease all ignition advances? Also, how crucial is the air temperature sensor in the AFM...that only controls the fueling correct?

If so, it is not a HUGE deal, I can fab something to simulate the AFM output based upon RPM & TPS. Thanks a million to nayone who knows the Motronic...oh if only I could track down Jim himself!

[DefactoM6]

If it's an Alpha-N type programmed setup (the MS) then it should work fine. However, given that you're not running a full MS, i'd say it will pull timing....

[bmwman91]

MS can do Alpha-N, but I will be running a Speed-Density setup as that is much more common & easier to tune (on a street car anyway). Anyone know where Jim C usually lurks around here?

[e34m535t]

I was told that the Motronic 1.3(in e34 535i, and e30 325i's etc..)'s Air Flow Voltage has no effect on Ignition Timing. I didnt think about the air temp sensor in the afm for timing, I KNOW it is used for fuel, and i Dont think it effects timing(i hope it doesnt )

PS: If you can use the same type of Air Inlet Temp Sensor for Megasquirt, then you could just wire the Motronic and MS to the same one.

[bmwman91]

Well, the inlet air temp sensor is a part of the stupid AFM that is in there, so when the AFM goes the sensr goes. The sensor is not a big deal, I have the correct GM ones for the MS and will put them where needed easily.
The E30 325 guys have it easy...their engines use distributors & the computer cannot do anything about the timing. The M42 uses individual coil packs, each controlled individually by the Motronic (1.7 I BELIEVE in my case, ver. 175). I am just not 100% sure about how the Motronic calculates load. I have done some more reading here & there & seen somethign about it using RPM & TPS as proxy inputs for load is the AFM is not present...I just need to know if that will cause the Motronic to retard the maps a bunch because it is in some sort of "limp mode." Aah, the joys of being the first one to do something to a particular engine.